Zepzelca fails key lung cancer trial, Pharma Mar plunges 22%

Jazz Pharmaceuticals' Zepzelca (lurbinectedin) failed to improve overall survival in a Phase 3 trial for relapsed small cell lung cancer, missing the primary endpoint and sending partner Pharma Mar's shares down 22 percent.

"Relapsed SCLC is an aggressive cancer with a poor prognosis and patients continue to need treatment options," Rob Iannone, executive vice president and global head of research and development at Jazz Pharmaceuticals, said in a statement. "Based on the strength of the IMforte trial results, we believe its most beneficial use is in the first-line maintenance setting."

The LAGOON trial enrolled 724 patients across more than 200 sites globally, testing Zepzelca as monotherapy and in combination with irinotecan against a control arm of topotecan or irinotecan. Patients on Zepzelca alone lived a median 8.7 months, while those on the combination lived 10.9 months, compared with 10.7 months in the control group. The hazard ratio for Zepzelca monotherapy versus control was 1.190, meaning patients on the drug had a 19 percent higher risk of death than those on standard care. In patients without a history of central nervous system metastases, median overall survival was 9.6 months for Zepzelca alone, 11.1 months for the combination and 10.7 months for the control.

Treatment-related adverse events occurred in 78.5 percent of patients on Zepzelca alone, compared with 95 percent on the combination and 93.8 percent on the control. Grade 3 or higher adverse events were 35 percent for Zepzelca monotherapy, 62.6 percent for the combination and 64.4 percent for the control, indicating a favorable safety profile for the single-agent arm.

Zepzelca holds accelerated approval from the US Food and Drug Administration as a second-line treatment for advanced SCLC, an aggressive form of lung cancer that accounts for about 13 percent of all lung cancer cases in the US. The drug received full approval in October 2025 for first-line maintenance use in combination with Roche's immunotherapy Tecentriq (atezolizumab), based on the Phase 3 IMforte trial that showed a 46 percent reduction in the risk of disease progression or death and a 27 percent reduction in the risk of death.

Jazz has shared the LAGOON results with the FDA and will discuss next steps regarding post-marketing requirements for the second-line indication. The company said the results do not affect its 2026 financial guidance. Jazz shares fell 2 percent in New York trading, while Madrid-listed Pharma Mar dropped 22 percent, reflecting the drug's greater weight in the Spanish biotech's pipeline.

The failed confirmatory trial puts the second-line accelerated approval at risk, though the first-line maintenance indication remains unaffected. Investors will watch for the FDA's decision on whether Zepzelca can retain its second-line label, a process that could take several months.

This article is for informational purposes only and does not constitute investment advice.